Substrate bias effects on collector resistance in SiGe heterojunction bipolar transistors on thin film silicon-on-insulator

An analytical expression for the collector resistance of a novel vertical SiGe heterojunction bipolar transistor (HBT) on thin film silicon-on-insulator (SOI) is obtained with the substrate bias effects being considered. The resistance is found to decrease slowly and then quickly and to have kinks with the increase of the substrate-collector bias, which is quite different from that of a conventional bulk HBT. The model is consistent with the simulation result and the reported data and is useful to the frequency characteristic design of 0.13 mu m millimeter-wave SiGe SOT BiCMOS devices.